Abstract CDC recommends both the 23-valent pneumococcal polysaccharide vaccine (PPSV23) and the 13-valent pneumococcal conjugate vaccine (PCV13) for adults aged ?65 years. However, PCV13 use in seniors, now rec- ommended in the immunocompetent based on shared decision making, may not substantially add to indirect (herd immunity) protection from childhood PCV13 use; recent analyses show use of both vaccines to be expen- sive with little added health benefit. Underserved minority adults, who are at greater risk, are less often vac- cinated and more often infected with non-vaccine pneumococcal serotypes. In all US adults, non-vaccine sero- type disease accounts for 40-49% of pneumococcal disease and vaccine uptake remains suboptimal. To address these issues, more serotypes are being added to conjugate vaccines while policymakers debate the need for adult conjugate use, given childhood vaccination indirect effects. An adult-formulated vaccine to improve pro- tection could be considered. Strategies to improve adult vaccination uptake are underused but could be the preferred way to improve pneumococcal disease protection, particularly in underserved minority seniors. To investigate, we will use decision analysis modeling to examine changes in recommended vaccines and in- tervention programs to address suboptimal vaccination strategies and low vaccine uptake. This effort will elu- cidate strategies to: a) improve pneumococcal disease protection in all older adults and b) decrease vaccination and disease disparities in underserved minorities. Potential changes in adult pneumococcal disease due to ad- ditional indirect childhood vaccination effects will be examined. We will synthesize available data and per- form projections with rigorous modeling of uncertainty to assist policymaking and inform research resource allocation. Potential changes to pediatric and adult vaccine formations will be modeled. Specific aims are to: 1) estimate the impact of higher valency conjugate vaccines on pneumococcal disease in children and resulting indirect effects on disease incidence and serotype distribution in US seniors; and 2) compare pneumococcal vaccination strategies in seniors, while accounting for childhood vaccination effects, examining higher valency vaccines, adult-formulated vaccine, and PPSV23 only, with and without programs to increase vaccine uptake. Vaccination strategies in underserved minority and general population cohorts will be compared via Markov model-based cost-effectiveness analysis, with probabilistic sensitivity analysis and value of information analy- sis to determine favored strategies and identify valuable areas for future research. We will also innovatively consider an adult-formulated conjugate vaccine designed to mitigate racial disease disparities. Since CDC vac- cination evaluations increasingly consider economic analyses, analysis results can be used, as previously, to assist vaccination recommendation decisions and potentially change policy to better protect the underserved.